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Feline Heartworm Disease Nia is an 11 year old, domestic, indoor-only female cat that has been a patient at Paws of the Rockies for about 2 years. Nia has a history of stomatitis, an immune mediated condition, which causes swelling, sores, redness, halitosis and pain of the oral tissues. Stomatitis can be a very difficult disease to manage as therapy is geared towards decreasing the inflammation in the mouth generally through the use of steroids (anti-inflammatory medication) and regular dental cleanings. Nia came in for an examination several months ago because her owner was concerned that she was not eating well and she was beginning to lose weight. She was also vomiting excessively. The owner was concerned, as were we, that her stomatitis was becoming unmanaged. Her physical exam showed severe swelling, redness and oral pain. Also, on her physical exam a heart murmur was diagnosed. We discussed several causes of heart murmurs in cats. We proceeded to perform an extensive blood work panel and urinalysis on Nia, ruling out hyperthyroidism, a common cause of murmurs in cats. Our plan for Nia was to determine first what was the cause of the murmur. Once we could determine this, we would proceed with our plan for treating Nia’s mouth disease. At this point, since the steroids were failing to control the disease, and since we were limited in our abilities to medicate her, we were now at the point of aggressive therapy. We would need to proceed with a full mouth extraction. Extracting all of the teeth is considered an aggressive approach, but a good percentage of cats do extremely well and in some cases the stomatitis will completely resolve. When Nia’s laboratory results came back completely normal, we referred her to CSU Cardiology service for a further workup of her heart. Her heart was actually functioning very well but, interestingly, CSU cardiology service diagnosed Nia with heartworm disease.
Nia’s case is important and interesting for several reasons: 1.) You will not find what you do not look for. Heartworm disease is uncommon in cats in Colorado, but can be a cause of hypertension and a heart murmur. The ultrasound that was performed on Nia’s heart actually visualized adult heartworms. 2.) It is important to look outside the box. It can be easy to focus on the disease at hand. Stomatitis is a serious medical condition in cats and can be difficult to manage and can be a cause of weight loss in cats. It is important, as we did, to pursue further testing. Even if blood work and a urinalysis were done recently, it is important to recheck blood work. Laboratory results can change quickly, from week to week or day to day. 3.) Different diseases can present similarly. Weight loss and vomiting can be common symptoms of many diseases in cats. It is important to perform a thorough workup for any chronic condition. 4.) This reminds us that feline heartworm disease is challenging to diagnose as well as treat. The disease can be serious and life threatening. Most importantly, this reminds us tat a strictly indoor lifestyle does not protect cats from contracting heartworm disease. Once Nia was seen at CSU cardiology, she received the go-ahead for her dental procedure. Twenty teeth were extracted during her procedure. Nia initially did have a rough recovery from such an aggressive procedure. Now it is has been several months since her dental procedure. Her mouth looked completely normal 8 weeks after her procedure. She does no longer have to receive steroid injections. Her owner reports that she is eating well and grooming herself normally again. Nia is still receiving Interceptor, a monthly heartworm preventative. Eventually, the adult heartworms will die due to their natural life span. We hope that Nia will continue to feel well and that her quality of life continues to thrive. (1) Antech Diagnostics News March 2007
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Occasionally antibiotics are used to control the oral infection that can commonly occur with this disease. Uncontrolled stomatitis can eventually lead to tooth loss, mouth pain, oral infections and weight loss because patients will cease to eat. Over the last few years, Nia’s therapy for her stomatitis consisted primarily of long-acting steroid injections to control the inflammation in her mouth. We opted to treat Nia with injectable steroids because her owner was concerned that she would not be able to medicate her with any oral or topical medications. Nia would just not tolerate the handling and could sometimes become “naughty”.
The first cases of feline heartworm disease were first reported in the 1920s in the United States. Heartworm disease is not as commonly associated with cats as it is with dogs. Cats are susceptible hosts but are not the natural hosts for heartworm disease. Therefore, they seem to be more resistant to infection than their canine counterparts. Because they are more resistant, cats usually only have 1-2 adult heartworms present, compared to the dozens that dogs can accommodate. For this reason, the clinical symptoms cats exhibit are often non-existent or are misdiagnosed as something else (asthma or allergic bronchitis). Feline heartworm disease has been shown to be present in 0-19% of cats in shelters across the US, which is about 5-20% of the infection rate seen in a parallel group of dogs. In addition, many infected cats are asymptomatic for the disease. Some symptoms include difficulty breathing, coughing, vomiting and unfortunately sudden death In addition, testing cats for heartworm disease is extremely difficult. Often there are a high percentage of false negative results. Heartworm antibody, heartworm antigen, ultrasound, radiographs, and blood work may all need to be performed to achieve a diagnosis. Once a diagnosis is made, treatment options are limited. Cats are not as easily treated for the disease as dogs are. Adult heartworm treatment can be life threatening for a cat, even though they have a “light infection”. The goal of feline heartworm disease therapy is to prevent the adult heartworms from reproducing. Therefore a monthly heartworm preventative is given for the lifetime of the cat. (1)